Classifying generated samples with Wasserstein-GAN as real or fake
My suggestion is to compare the critics rating for the real data and the generated data. Compute the mean of the ratings on real data to get some kind of threshold. If your critic is designed so that a high rating indicates a real sample, then generated data with ratings greater than the mean of the ratings of the real data could be viewed as good enough to fool the critic at that point in training.
This might be a too harsh criteria, but you will at least not accept poorly generated data.